A multi-blade centrifugal fan including a volute shaped casing is an example of a known blower. The multi-blade centrifugal fan includes an impeller that has many blades at the periphery thereof and that is rotatably disposed in the volute shaped casing. Outside air is sucked into the impeller through an air inlet that opens in a side surface of the volute shaped casing. The air is discharged from the impeller that rotates through spaces between the blades in the volute shaped casing, and is blown an air outlet of the volute shaped casing. The impeller includes a disk-shaped backing plate adjacent to a motor, a ring-shaped rim adjacent to the air inlet of the volute shaped casing, and a plurality of blades that connect the backing plate and the rim (see, for example, Patent Literature 1).